The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC design and material have produced generations of ICs where each generation has smaller and more complex circuits than previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased.
Manufacturing of waveguide structure has experienced exponential growth. The waveguide structures have attracted a lot of attentions because of its process availability and manufacturing feasibility. In general, a light is confined in the waveguide structure by a total internal reflection from the waveguide walls. However, the manufacturing of the waveguide structure has challenges.